[HBASE-10324] refactor deferred-log-flush/Durability related interface/code/naming to align with changed semantic of the new write thread model

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.98.0, 0.99.0
• Component/s: Client, regionserver
• Hadoop Flags: Reviewed
• Release Note: In HTableDescriptor, isDeferredLogFlush() and setDeferredLogFlush() are replaced by isAsyncLogFlush() and setAsyncLogFlush(), respectively.
• Assignee: Honghua Feng
• Reporter: Honghua Feng
• Created: 12/Jan/14 09:24
• Updated: 21/Feb/15 23:31
• Resolved: 14/Jan/14 17:58

Description

By the new write thread model introduced by HBASE-8755, some deferred-log-flush/Durability API/code/names should be change accordingly:
1. no timer-triggered deferred-log-flush since flush is always done by async threads, so configuration 'hbase.regionserver.optionallogflushinterval' is no longer needed
2. the async writer-syncer-notifier threads will always be triggered implicitly, this semantic is that it always holds that 'hbase.regionserver.optionallogflushinterval' > 0, so deferredLogSyncDisabled in HRegion.java which affects durability behavior should always be false
3. what HTableDescriptor.isDeferredLogFlush really means is the write can return without waiting for the sync is done, so the interface name should be changed to isAsyncLogFlush/setAsyncLogFlush to reflect their real meaning